pythonによるテキストファイルの分割の方法

import os

out_dir = './output/'
os.makedirs(out_dir, exist_ok = True)

# 愚直実装
with open("points.txt") as f:
    lines = f.readlines()
    for i in range(len(lines) // 2):
        with open(os.path.join(out_dir, f"{i}.txt"), "w") as output:
            index = lines[i * 2]
            text = lines[i * 2 + 1]
            output.writelines(lines[i * 2: (i + 1) * 2])

# 最初でまとめる方法
with open("points.txt") as f:
    lines = f.readlines()
    lines = [lines[i: i + 2] for i in range(0, len(lines), 2)]
    for i, (index, text) in enumerate(lines):
        with open(os.path.join(out_dir, f"{i}.txt"), "w") as output:
            output.writelines(index + text)

def getKigu(file):
    with open(file,"r", encoding="UTF-8") as fd1:
　　　　　lines =　iter(fd1.readlines())
　　　　　for no, (ki,gu) in enumerate(zip(lines,lines)):
             yield str(no), ki,gu

for no, ki, gu in getKigu("points.txt"):
    with open(no + ".txt","w", encoding="UTF-8") as fd2:
   　　 fd2.write(ki)
　　　　 fd2.write(gu)
   　　 fd2.flush()